Perplexing Platy Species  9/25/09
I was looking up species of platy fish the other night and ran into a perplexing puzzle.
<Oh?>
I know Xiphophorus is the class platys, variegated platys, swordtails, and hybrids of the three are placed under.
<Indeed. In fact the Swordtails and Platies sold in pet stores are probably all hybrids of one sort or another. To get pure-bred species of either Platy, Variatus Platy, or Swordtail you need get wild-caught fish or fish bred by dedicated hobbyists.>
Yet I ran into terms such as sp, sp., and 35RD which I did not understand.
<The word "sp." simply means "species", and is how scientists describe a specimen that they cannot, for whatever reason, identify to species level.
In some case the animal concerned does indeed belong to a recognised species, but the scientist just wasn't able to make that identification, lacking the tools, skills or materials. If you found a baby fish in a canal somewhere in Mexico, and you recognised it was some sort of Xiphophorus, but it was too young to identify to species level, you'd call it "Xiphophorus sp.". In other situations, you might find a whole bunch of Xiphophorus you weren't able to identify, and though you couldn't name the species, you could tell that there was more than one species there. In this case, you'd call them "Xiphophorus spp.", meaning Xiphophorus species plural. In other instances, the "sp." or "spp." refers to the fact that these are new species, but you haven't formally identified them. While hobbyists might assume it's quite easy to name a new animal should you discover one, it's actually quite hard work. You have to carefully check the animal hasn't been discovered before, in particular taking care that the thing was reported decades ago and subsequently forgotten about because the description was published in an obscure or foreign language journal. You have to make sure you new animal isn't just an odd version of a familiar species; for example genetic mutations and physical damage can cause animals to look different to other members of their species. And
you'd be surprised how often male and female animals of the same species accidentally got described as different species! The whole process often takes years.>
One species that was listed was listed as Xiphophorus sp 35RD. Now here is where things really got confusing for me. What species of platy is Xiphophorus sp 35RD?
<It's a species of Xiphophorus known to be distinct, but as yet, not formally identified. Because the tropical fish trade often handles newly discovered fish soon after discovery, such fish appear in the shops before scientists give them formal names. So fish exporters give these fish temporary names, in this case, Xiphophorus sp. 35RD. I have no idea what the "35RD" stands for, but it's probably a collecting site or some such.>
Where was it found?
<Mexico, I'd imagine.>
Is it simply an outdated name of another platy, or is this its actual species name?
<It's a "placeholder name" until the fish gets a proper scientific name.
It's analogous to the L-number system used for catfish, where for example the species traded as L001 eventually became Pterygoplichthys joselimaianus.>
What does sp. and sp mean? I know sp. and sp can refer to a species name sometimes. But it does not say when sp or sp. is listed what species to which it is referring. Is it the southern platy, the swordtail, the variegated platy?
<None of the above.>
It simply does not say. And sp and sp. can also mean other things as well.
And what in the world does 35RD mean? Xiphophorus sp 35RD has a taxonomic number, but that is all the information I was able to get. Other than it is a member of the Xiphophorus family.
<Xiphophorus is a genus, not a family. The family is Poeciliidae. In any case, all Xiphophorus are very similar in terms of requirements: relatively cool water, around 22-24 C, hard, basic water chemistry. They're all herbivores, so an algae-based flake food is required. Some come from fast flowing waters (Swordtails) but most come from still water habitats; looking at the body shape is a clue here. If they're streamlined, they like fast water, if they're dumpy, like a Platy, slow-flowing water is better.>
If you have any more information on this species, or better yet a picture, please let me know.
<Not aware that Xiphophorus sp. 35RD is traded yet; certainly never seen a picture. But I can be fairly sure it's small, green, with an upturned mouth and a modest degree of sexual dimorphism -- like all the other (wild-type) members of its genus. Cheers, Neale.>